Belief That Caffeine Ingestion Improves Performance in a 6-Minute Time Trial Test without Affecting Pacing Strategy

This study aimed to analyze the placebo effect associated with caffeine ingestion on running performance. Methods: Thirteen recreationally trained males in long-distance running (age: 38.5 +/- 11.9 years, 11.0 +/- 8.8 years of running experience) performed a 6 min time trial test in each experimental condition (caffeine-informed/placebo ingested (placebo) and non-ingested (control)) separated by 7 days. The total distance covered was measured, and partial times of each 400 m were used to analyze the pacing strategy. Heart rate and kinematic variables were recorded for each split. In addition, the rate of perceived exertion and prevalence of caffeine side effects was measured using questionnaires. Results: Placebo ingestion improved running performance in the 6 min time trial test (1668 +/- 139 m placebo vs. 1642 +/- 158 m control, t = 2.49; p = 0.03; moderate ES = 0.69), while pacing, heart rate, RPE, and kinematic variables were similar between conditions (p > 0.05 in all cases). Minor side effects were reported. Conclusions: Beliefs of caffeine ingestion can improve running performance at speeds around maximal aerobic speed in recreationally trained runners without affecting pacing strategy so this "nutritional" strategy could be useful in competition scenarios. As a practical application, recreationally trained runners could improve approximate to 5 s in 1500 m or mile competitions.